linux-kernel - Re: [PATCH v2 3/5] thermal: devfreq_cooling: add new registration functions with Energy Model

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Message-ID: <20201202114909.GA1198@arm.com>
Date:   Wed, 2 Dec 2020 11:49:10 +0000
From:   Ionela Voinescu <ionela.voinescu@....com>
To:     Lukasz Luba <lukasz.luba@....com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, rui.zhang@...el.com,
        amit.kucheria@...durent.com, daniel.lezcano@...aro.org,
        orjan.eide@....com, robh@...nel.org,
        alyssa.rosenzweig@...labora.com, steven.price@....com,
        airlied@...ux.ie, daniel@...ll.ch
Subject: Re: [PATCH v2 3/5] thermal: devfreq_cooling: add new registration
 functions with Energy Model

On Wednesday 02 Dec 2020 at 11:14:02 (+0000), Lukasz Luba wrote:
> Hi Ionela,
> 
> On 12/2/20 10:24 AM, Ionela Voinescu wrote:
> > Hi Lukasz,
> > 
> > On Wednesday 18 Nov 2020 at 12:03:56 (+0000), Lukasz Luba wrote:
> 
> [snip]
> 
> > > +	struct device_node *np = NULL;
> 
> [snip]
> 
> > > +
> > > +	if (dev->of_node)
> > > +		np = of_node_get(dev->of_node);
> > > +
> > 
> > Should np be checked before use? I'm not sure if it's better to do the
> > assign first and then the check on np before use. It depends on the
> > consequences of passing a NULL node pointer later on.
> 
> The np is actually dev->of_node (or left NULL, as set at the begging).
> The only meaning of the line above is to increment the counter and then
> decrement if CONFIG_OF_DYNAMIC was used.
> The devfreq_cooling_register() has np = NULL and the registration can
> handle it, so we should be OK here as well.
> 

Yes, I just wanted to make sure later registration can handle np = NULL,
or whether we need to bail out.

In this case, you can drop both ifs - for (dev->of_node) before get and
for np before put below, as of_node_get/of_node_put can handle NULL
pointers themselves.

Thanks,
Ionela.

> > 
> > > +	cdev = of_devfreq_cooling_register_power(np, df, dfc_power);
> > > +
> > > +	if (np)
> > > +		of_node_put(np);
> > > +
> 
> [snip]
> 
> > > 
> > 
> > Otherwise it looks good to me:
> > 
> > Reviewed-by: Ionela Voinescu <ionela.voinescu@....com>
> 
> Thank you for the review.
> 
> Regards,
> Lukasz
> 
> > 
> > Ionela.
> >